Apparatus for mass die testing

ABSTRACT

A semiconductor wafer includes a set of dice under test connected together by a plurality of signal buses; and at least one test die designed for carrying out tests of the dice under test, having a set of pads to be connected to one or more probes of an external test apparatus, and at least one multiplexer connected with the set of dice under test via the signal buses, such that the test die is capable of receiving signals from the external test apparatus to select any die under test within the set via the multiplexer and the signal buses without repositioning the probes.

BACKGROUND

The present invention relates generally to integrated circuit (IC) designs, and more particularly to an apparatus for testing a large number of dice on a semiconductor wafer without repositioning test probes.

A semiconductor wafer typically contains a large number of dice constructed on a round-shaped semiconductor substrate. Each die embodies a complex integrated circuit formed by semiconductor processing technology, such as chemical vapor deposition, thermal oxidation, ion implantation, lithography, etching, and metallization, to carry out certain functionalities. These dice need to be tested to determine whether they meet predefined specifications, before they can be separated from the wafer for individual package. Conventionally, each die may include one or more pads that can be used to form electrical contacts with test probes of an external test machine. The test machine sends out test signals and receives resultant signals to and from the die under test (DUT) via the test probes and the pads. The resultant signal contains information with respect to the DUT, and can be further analyzed by the test machine to determine whether the DUT meet those predefined specifications.

One drawback of the conventional die testing scheme is that it is very time consuming. Every time when the test machine tests a new die, the test probes need to be repositioned from a previous DUT to form electrical contacts with the pads of the new die. Every repositioning of probes may take seconds, and a semiconductor wafer usually contains tens to tens of thousands of dice. As a result, a complete test for a semiconductor wafer usually requires a long time, which often represents a significant portion of the manufacturing cost for each die. As the semiconductor processing technology advances, the number of dice on a semiconductor wafer increases significantly, and therefore the manufacturing cost of die also increases dramatically due to the prolonged die testing procedure.

For example, conventional probe testing can only be performed on a few unsorted dice, typically less than 20 DUTs, for each time that the probes are positioned. In order to perform tests on a larger number of DUTs, the probes need to be repositioned. Supposing that 80,000 DUTs on a semiconductor wafer need to be tested, a really long period of time will be needed just for repositioning the probes. In the time-conscious of semiconductor industry, the cost incurred by the testing time is often unacceptable.

As such, desirable in the art of IC designs is an apparatus for testing a large number of dice on a semiconductor wafer without repositioning test probes.

SUMMARY

The present invention discloses an apparatus for testing a large number of dice on a semiconductor wafer without repositioning test probes. One embodiment of the invention is described herein for explaining the principles of the invention. In the embodiment, the apparatus is embodied as a semiconductor wafer, which includes a set of dice under test connected together by a plurality of signal buses; and at least one test die designed for carrying out tests of the dice under test, having a set of pads to be connected to one or more probes of an external test apparatus, and at least one multiplexer connected with the set of dice under test via the signal buses, such that the test die is capable of receiving signals from the external test apparatus to select any die under test within the set via the multiplexer and the signal buses without repositioning the probes.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of a built-in self test (BIST) die used for multiplexing test signals to a selected DUT on a semiconductor wafer in accordance with one embodiment of the present invention.

FIG. 2A illustrates a set of DUTs, among which a BIST die is implemented, in accordance with one embodiment of the present invention.

FIG. 2B illustrates a diagram showing a DUT connected to the BIST die via signal buses routed along the scribe lines in accordance with one embodiment of the present invention.

FIG. 2C illustrates a cross-sectional view of the seal ring in accordance with one embodiment of the present invention.

FIG. 3A illustrates a block diagram of a test system designed for testing a plurality of RF dice in accordance with one embodiment of the present invention.

FIG. 3B illustrates an impedance matching circuit that can be implemented in a matching module of the test system shown in FIG. 3A in accordance with one embodiment of the present invention.

FIG. 3C illustrates a transformer circuit that can be implemented in a matching module of the test system shown in FIG. 3A in accordance with one embodiment of the present invention.

DESCRIPTION

This invention describes an apparatus for testing a large number of dice on a semiconductor wafer without repositioning test probes. The following merely illustrates various embodiments of the present invention for purposes of explaining the principles thereof. It is understood that those skilled in the art will be able to devise various equivalents that, although not explicitly described herein, embody the principles of this invention.

FIG. 1 illustrates a block diagram of a BIST die 100 implemented for performing circuit probing test for RF dice on a semiconductor wafer in accordance with one embodiment of the present invention. It is noted that the RF dice are used merely as an example to explain the principles of the invention, which can be applied to other types of dice, and by no means are limited to RF dice.

The BIST die 100 includes a multiplexer 102, a set of test probing pads 104, a set of address probing pads 106, and a set of power supply probing pads 108. The probing pads 104, 106 and 108 can be collectively referred to as a pad array 110. The multiplexer 102 has a plurality of ports 102 a through 102 j connected to a plurality of signal buses, including the buses extended to the pad array 110 and the buses extended to other dice on the semiconductor wafer. During test operation, the probing pads 104, 106, and 108 are further coupled to a test apparatus (not shown in this figure), which selects one or more dice on a semiconductor wafer for testing. The multiplexer 102 is also coupled with signal buses 102 b and 102 a that are placed on a X-direction scribe line and a Y-direction scribe line, respectively, such that a specific DUT may be selected by the multiplexer 102 with address information received at the address probing pads 106 from the test apparatus. When a particular DUT is selected by the BIST die 100, it can be powered up quickly using the power received at the power supply probing pads 108 from the test apparatus or using the DC power converted from an RF signal generated by the test apparatus with the DUT or the BIST die. Various tests can be performed on the selected DUT based on the test signals received at the test probing pads 104 from the test apparatus. In this embodiment, the BIST die 100 is embedded among the dice under test on the semiconductor wafer.

In another embodiment, the multiplexer 102 can be implemented on a probe card, instead of a semiconductor wafer. The multiplexer 102 on the probe card includes a number of ports that allow the multiplexer to couple with a test apparatus for receiving and transmitting test signals, address signals, and power signals there between. The probe card further includes a number of probes for forming electrical contacts with the DUTs on the semiconductor wafer. In this embodiment where the probe card is used to test RF DUTs, the probes at minimum includes two RF probes for passing RF test signals, two power probes for supplying power, and three digital probes for passing address signals. The semiconductor wafer can be implemented with a number of pads that function as accesses to the DUTs through signal buses routed along the scribe lines. The probes can be placed on the pads of the semiconductor wafer to form one or more signal paths among the DUTs and the test apparatus. The test apparatus can select one or more DUTs, sends out RF test signals, and receives resultant signals from the DUTs for further analysis to determine whether they meet certain predefined specifications.

FIG. 2A illustrates a set of DUTs 200, among which a BIST die 100 as shown in FIG. 1 is implemented in accordance with one embodiment of the present invention. The set of DUTs 200, for example, includes 99 DUTs 202 arranged in a 10×10 array. The multiplexer within the BIST die 100 is connected to each DUT within the set 200 through signal buses routed along the scribe lines, which are shown as the dark lines in this figure. Each DUT 202 includes a set of tacks 204 that are extended from the circuit region of the DUT 202 to its surrounding scribe lines to form electrical connections between the electrical components within the DUT 202 and the signal buses on the scribe lines.

When a DUT is being tested, a test apparatus (not shown in the figure) generates testing signals, address signals, and power signals to the multiplexer within the BIST die 100 through contacts formed by its probes and the probing pads on the BIST die 100. The multiplexer utilizes the information carrier by the address signals to select one or more DUTs for testing. Power and test signals are passed onto the selected DUTs via the signal buses. The set of tacks extended from the selected DUT to the scribe line allow the DUT to receive test signals and power from the signal buses. It is noted that although FIG. 2A only shows 99 DUTs, in real applications, the BIST die 100 may be implemented among a set of DUTs with a much larger number, such that the probes will not need to be repositioned for any DUT selected from the set.

FIG. 2B illustrates an enlarged diagram 206 showing the DUT 202 and the multiplexer 102 of the BIST die are connected via signal buses along the scribe lines in accordance with one embodiment of the present invention. The multiplexer 102 is coupled with the signal buses along an X scribe line 230 and a Y scribe line 232, and it is designed to select a DUT within the array based on the address information provided by address signals received at the address probing pad from an external test apparatus. The multiplexer 102 has a number of ports designed for receiving signals from the probes of the test apparatus that are in contact with its probing pads. In this embodiment, the multiplexer 102 includes a set of RF testing signal ports 208, a set of address ports 210, and a set of power input ports 212. When the DUT 202 is selected using the address information received at the address ports 210, the multiplexer 102 will provide power and RF test signals received at its power and RF ports to the DUT 202 through the signal buses along the scribe lines. It is noted that in one embodiment, the DUT 202 can convert RF power received from the multiplexer 102 into DC power for operation. In such case, the multiplexer 102 will provide only the RF signals without the power signals.

The integrated circuits in the DUT 202 is surrounded by a seal ring 214 that is designed to protect the electrical components within the DUT 202 from the outside environment, once it is cut out from the semiconductor wafer. The DUT 202 is coupled with the signal buses along the X scribe line 230 and a Y scribe line 234 via the tacks disposed there between. The tacks, not shown in FIG. 2B, are metal traces deposited at the edges of the DUT 202, and extended to the signal buses on the scribe line. These metal traces are designed to deliver signals, such as the RF test signals, from the multiplexer 102 into the DUT 202, and they are laid on the space of the scribe lines that will eventually be cut off when the dice are separated. In order for the connection to be made between the DUT 202 and the signal buses, a plurality of feed-through paths 216 are constructed through the seal ring 214 for the metal traces to contact with the electrical components within the DUT 202. The DUT 202 has a number of ports used for receiving signals from the tacks passing though the seal ring 214.

FIG. 2C illustrates a cross-sectional view of the seal ring 214, across which the feed-through paths 216 are disposed, in accordance with one embodiment of the present invention. The feed-through paths 216 can be formed on any metallization layer. In another embodiment, multiple feed-through paths 216 may be used for complex applications, where the feed-through paths 216 are electrically connected with one another through vias, if required.

FIG. 3A illustrates a block diagram of a test system 300 designed for testing a large quantity of RF dice on a semiconductor wafer 306 in accordance with one embodiment of the present invention. The test system 300 includes a test apparatus 302 and a probe array 304. The test apparatus 302 further includes a plurality of matching modules 308, a plurality of RF testers 310, and a control device 312.

In this embodiment, the semiconductor wafer 306 contains a large number of RF dice grouped into hundreds of sets of DUTs. Each set of DUTs includes at least one test chip such as the BIST die 100 shown in FIG. 1. Several thousands of DUTs with the set can be selected and tested for each placement of probes based on the address information provided to the BIST die 100 by the control device 312 via an addressing bus 313 and the probe array 304. This addressing bus 313 essentially provides X and Y coordinates that are designated by the control device 312 and received by the probe array 304. The probe array 304 provides physical connections to the BIST die 100 which, based on the X and Y coordinates provided by the addressing bus 313, selects one or more DUTs for testing. During test operation, RF test input signals are provided to the selected DUTs, and the output test signals from the selected DUTs then travel through the multiplexer within the BIST die and the probe array 304 to reach the matching modules 308 via a set of RF cables 304C. The matching modules 308 are designed to couple the RF signals between the probe array 304 and the RF testers 310. Thus, the signals output from the selected DUTs can be sent to the RF tester 310 and control device 312 for further analysis to determine whether they meet certain predetermined specifications.

FIG. 3B illustrates an impedance matching circuit 314 that can be implemented in the matching module 308 shown in FIG. 3A in accordance with one embodiment of the present invention. The impedance matching circuit 314, which includes inductors 316, 318 and a capacitor 320, is implemented between an antenna interface 324 coupled to the probe array 304 shown in FIG. 3A and an RF tester 322. The inductors 316 and 318 are serially connected with the capacitor connected there between in parallel in order to couple RF signals between the antenna interface 324 and the RF tester 322. The matching circuit 314 allows RF signals to be converted into DC signals, thereby allowing the test apparatus 302 to test RF dice on the semiconductor wafer 306, as shown in FIG. 3A.

FIG. 3C illustrates a transformer circuit 326 that can also be implemented in the matching module 308 shown in FIG. 3A in accordance with one embodiment of the present invention. The transformer circuit 326 includes two inductors 328 and 330, and is implemented between an antenna interface 334 coupled to the probe array 304 shown in FIG. 3A and a RF tester 332. The transformer circuit 326 allows RF signals to be converted into DC signals, thereby allowing the test apparatus 302 to test RF dice on the semiconductor wafer 306, as shown in FIG. 3A.

One of the advantages of the invention is that the time needed for testing a semiconductor wafer can be reduced significantly due to a reduced number of probe repositioning. For example where a semiconductor wafer has 79,920 dice, the dices can be grouped into 555 sets with each having 114 dice. In this example, the probes only need to be repositioned 555 times to complete the test of the wafer. However, in a conventional test scheme, the probes may need to be repositioned 79,920 times to complete the test. As a result, the proposed test scheme can reduce the test time significantly, thereby reducing the manufacturing costs of the wafer. Another advantage of the invention is that the proposed scheme with the antenna coupling device can be used to test RF dice, which may not be readily tested by conventional test schemes.

The BIST dice and regular dice can be constructed on a semiconductor wafer by various processes. In one embodiment of the present invention, a mask set is used to form both the BIST dice and regular dice on the semiconductor wafer. During photolithography processes, a layer of photoresist material is coated over the wafer, and then exposed to light for transferring circuit patterns from the mask set to the photoresist layer. The transferred patterns include those for the regular dice and those for the BIST dice. Thus, one mask set would be sufficient. In another embodiment of the present invention, two mask sets are used to form the BIST dice and regular dices on a semiconductor wafer. One of the mask sets includes patterns for making the regular dice and the other mask set includes patterns for making the BIST dice. As such, two separate photolithography processes will be needed to transfer the patterns from the two mask sets to the photoresist layer coated on the semiconductor wafer for forming the two types of dice.

The above illustration provides many different embodiments or embodiments for implementing different features of the invention. Specific embodiments of components and processes are described to help clarify the invention. These are, of course, merely embodiments and are not intended to limit the invention from that described in the claims.

Although the invention is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention, as set forth in the following claims. 

1. A semiconductor wafer comprising: a set of dice under test (DUT) connected together by a plurality of signal buses; and at least one built-in self test (BIST) die including at least one multiplexer designed for multiplexing test signals to a selected DUT on the semiconductor wafer for carrying out tests of the dice under test, the BIST die having a set of pads to be connected to one or more probes of an external test apparatus, and wherein the at least one multiplexer being connected with the set of dice under test via the signal buses, such that the BIST die is capable of receiving signals from the external test apparatus to select any die under test within the set via the multiplexer and the signal buses without repositioning the probes.
 2. The semiconductor wafer of claim 1 wherein the set of pads comprises one or more test probing pads for receiving test signals from the external test apparatus via the probes.
 3. The semiconductor wafer of claim 1 wherein the set of pads comprises one or more address probing pads for receiving address signals indicating an address of at least one die under test from the external test apparatus via the probes.
 4. The semiconductor wafer of claim 1 wherein the set of pads comprises one or more power supply probing pads for receiving power from the external test apparatus via the probes.
 5. The semiconductor wafer of claim 1 wherein the signal buses are routed along scribe lines among the dice under test.
 6. The semiconductor wafer of claim 5 wherein each die under test has a seal ring with one or more feed-through paths, through which one or more tacks are disposed to form electrical connections between the signal buses and electrical components within the seal ring.
 7. The semiconductor wafer of claim 6 wherein the die under test is a radio frequency (RF) chip.
 8. A test system comprising: a semiconductor wafer having a set of dice under test connected together by a plurality of signal buses, and at least one built-in self test BIST die designed for carrying out tests of the dice under test, wherein the BIST includes at least one multiplexer; a set of probes connected to one or more pads on the BIST die; a test apparatus coupled to the probes for sending test signals to one or more selected dice under test, and for receiving output signals from the selected dice under test for analysis through the multiplexer, wherein the multiplexer is connected to the dice under test via the signal buses, such that the BIST die is capable of receiving signals from the test apparatus to select any die under test within the set without repositioning the probes.
 9. The system of claim 8 wherein the pads comprise one or more test probing pads for receiving test signals from the test apparatus via the probes, one or more address probing pads for receiving address signals indicating an address of at least one die under test from the test apparatus via the probes, and one or more power supply probing pads for receiving power from the test apparatus via the probes.
 10. The system of claim 8 wherein the signal buses are routed along scribe lines among the dice under test.
 11. The system of claim 10 wherein each die under test has a seal ring with one or more feed-through paths, through which one or more tacks are disposed to form electrical connections between the signal buses and electrical components within the seal ring.
 12. The system of claim 8 wherein the regular die is a radio frequency (RF) chip.
 13. The system of claim 12 wherein the set of probes comprises at least two test signal probes for passing test signals, at least three address probes for passing address signals to select one or more dice under test, and at least two power probes for providing the test die with power.
 14. The system of claim 13 wherein the test apparatus comprises a control device coupled to the probes for generating the address signals.
 15. The system of claim 14 wherein the test apparatus comprises at least one RF tester coupled between the control device and at least one matching module that couples RF signals between the RF tester and an antenna interface for signals output from the test die.
 16. The system of claim 15 wherein the matching module is a transformer or an impedance matching circuit constructed by at least one inductor and at least one capacitor.
 17. A probe card for testing a set of dice under test on a semiconductor wafer, comprising: at least one set of probes to be connected to one or more pads or a built-in self test (BIST) die on the semiconductor wafer for providing accesses to the dice under test via signal buses there among; at least one multiplexer located within the BIST die and coupled to the probes, having one or more ports for receiving and sending signals from and to an external test apparatus; wherein when the test probes are in contact with the pads and the ports are connected to the external test apparatus, the external test apparatus can select any die under test within the set without repositioning the probes.
 18. The probe card of claim 17 wherein the probes comprises at least one radio frequency (RF) probes for passing RF test signals, at least two power probes for providing power, and at least three digital probes for passing address signals.
 19. The probe card of claim 17 wherein the signal buses are routed along scribe lines among the dice under test.
 20. The probe card of claim 17 wherein each die under test has a seal ring with one or more feed-through paths, through which one or more tacks are disposed to form electrical connections between the signal buses and electrical components within the seal ring. 